In recent years, RF radio signal receiving apparatus, especially RF pagers, have been widely accepted by industrial, commercial and private users because of the significant flexibility and convenience the RF pagers provide to the users in providing instant wireless communications. The RF communications link provided by the pagers eliminates the need for wired line telecommunications required in conventional telephone systems and permits the users to have the portable pagers that they can carry with them within the transmission range of the transmitting stations conveniently so that they can be reached at any instance. Using integrated circuitry and digital logic, it has been possible to provide more and more of optional features to the pagers. In spite of the additional features added to the pagers, it has been possible to reduce the size of the pagers even smaller, even to a size not much bigger than an ordinary fountainpen people carry with them.
Additional optional features that are provided in the more enhanced pagers include such features as a dual call option, an automatic reset option and a battery saver option.
A conventional minimum feature pager is of a design that typically detects incoming signal of a particular signal form, for example, five-tone codes, and that includes a switch which is used manually to turn on and off the pagers. Often, the conventional pager does not include a battery-saving feature; thus, they drain a substantial amount of battery energy and render the life of the pager short, or require replacement of the drained battery with a new battery, or recharging the drained battery quite frequently.
More recently-developed pagers are now provided with a battery saving feature which is designed to strobe portions of the receiving circuitry periodically to extend battery life. They are also provided with dual option circuitry permits it to respond to two different signals. This makes the pager adaptable to operate with the five-tone or six-tone signals utilized extensively in the paging systems in the marketplace. They are further provided with an automatic reset option feature that permits the pager to alert and reset the alert after a preset period and thereby quiet the pager after the preset period. This is in contrast with the conventional pager where the pager will continue to alert or beep until the operator resets the pager, thereby annoying bystanders.
For reasons of economy, it has been found to be advantageous to incorporate most or all of the optional features into the integrated circuits used in the pagers and to use elements external to the IC to select or disable selected optional features. To provide this selective enable and disable function, a circuitry, referred to as a code plug, pluggable to the pager circuitry and becomes part of the pager, has been developed. The code plug is designed to include circuitry which includes a programmable options section that may be programmed to suit the need of particular customers on optional features. Naturally, the more options programmed into the code plug, the more options are provided to the user when the code plug is plugged into the pager for use. Of course, it is desirable to relate the selling price of the pager to the number and type of options provided.
A consequence of this approach, however, is that it creates the temptation for users to try to devise ways of using the optional feature circuitry with code plugs of their own design or some suitable bypass scheme without having to pay for the additional charges for the receiving apparatus designed to cover expenses and costs incurred to the original manufacturer.